Factors of type II1 without non-trivial finite index subfactors
Abstract
We call a subfactor trivial if it is isomorphic with the obvious inclusion of N into matrices over N. We prove the existence of type II1 factors M without non-trivial finite index subfactors. Equivalently, every M-M-bimodule with finite coupling constant, both as a left and as a right M-module, is a multiple of L2(M). Our results rely on the recent work of Ioana, Peterson and Popa, who proved the existence of type II1 factors without outer automorphisms.
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